Poly[[diaquabis[μ-(2,4-dichlorophenoxy)acetato]calcium(II)] monohydrate]

In the title coordination polymer, {[Ca(C8H5Cl2O3)2(H2O)2]·H2O}n, the CaII atom is eight-coordinated by six O atoms from four different (2,4-dichlorophenoxy)acetate ligands and two water molecules, and displays a distorted square-antiprismatic coordination geometry. The compound forms an infinite zigzag chain through connection of the metal centers by (2,4-dichlorphenoxy)acetate ligands and hydrogen bonding of coordinated and interstitial water molecules. These chains are further hydrogen bonded with neighboring chains, forming a supramolecular network.

In the title coordination polymer, {[Ca(C 8 H 5 Cl 2 O 3 ) 2 (H 2 O) 2 ]Á-H 2 O} n , the Ca II atom is eight-coordinated by six O atoms from four different (2,4-dichlorophenoxy)acetate ligands and two water molecules, and displays a distorted square-antiprismatic coordination geometry. The compound forms an infinite zigzag chain through connection of the metal centers by (2,4-dichlorphenoxy)acetate ligands and hydrogen bonding of coordinated and interstitial water molecules. These chains are further hydrogen bonded with neighboring chains, forming a supramolecular network.

S1. Comment
In the structural investigation of 2,4-dichlorophenoxyacetate complexes, it has been found that the (2,4-dichlorphenoxy)acetate functions as a multidentate ligand [Song et al. (2006);Hao et al. (2006)], with versatile binding and coordination modes. In this paper, we report the crystal structure of the title compound, (I), a new Ca complex obtained by the reaction of (2,4-dichlorphenoxy)acetate and calcium chloride in an alkaline aqueous solution.
As illustrated in Figure 1, the Ca II atom exists in a distorted square-antiprismatic environment, defined by six O atoms from four different 2,4-dichlorophenoxyacetate ligands and two water molecules. The 2,4-dichlorophenoxyacetate ligands link the calcium ions to form infinite zigzag like chains, which are further stabilized by hydrogen bonding of the coordinated and interstitial water molecules O2W and O3W to carboxylate oxygen atoms (Table 1, Fig. 2). O1W, via a hydrogen bond to the ether oxygen atom O6, also stabilizes the chains, but also forms another intermolecular hydrogen bond to a water molecule O3W that is part of a neighboring chain, thus forming a supramolecular network of H-bonded chains.

S2. Experimental
A mixture of calcium chloride (1 mmol), 2,4-dichlorophenoxyacetate (1 mmol), NaOH (1.5 mmol) and H 2 O (12 ml) was placed in a 23 ml Teflon reactor, which was heated to 433 K for three days and then cooled to room temperature at a rate of 10 K h -1 . The crystals obtained were washed with water and dryed in air.

S3. Refinement
Carbon-bound H atoms were placed in calculated positions and were treated as riding on the parent C atoms with C-H = 0.93-0.97 Å, and with U iso (H) = 1.2 U eq (C). Water H atoms were tentatively located in difference Fourier maps and were refined with distance restraints of O-H = 0.84 Å and H···H = 1.39 Å, each within a standard deviation of 0.01 Å, and with

Figure 1
The structure of (I), showing the atomic numbering scheme. Non-H atoms are shown as 30% probability displacement ellipsoids.

Figure 2
A packing view of (I).  Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > σ(F 2 ) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.